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Metabolic engineering for the production of fat-soluble vitamins: advances and perspectives.
Yuan, P, Cui, S, Liu, Y, Li, J, Du, G, Liu, L
Applied microbiology and biotechnology. 2020;(3):935-951
Abstract
Fat-soluble vitamins are vitamins that are insoluble in water, soluble in fat, and organic solvents; they are found in minute amount in various foods. Fat-soluble vitamins, including vitamins A, D, E, and K, have been widely used in food, cosmetics, health care products, and pharmaceutical industries. Fat-soluble vitamins are currently produced via biological and chemical synthesis. In recent years, fat-soluble vitamin production by biotechnological routes has been regarded as a very promising approach. Based on biosynthetic pathways, considerable advances of α-tocopherol and β-carotenes have been achieved in transgenic plants and microalgae. Microbial fermentation, as an alternative method for the production of vitamin K and β-carotenes, is attracting considerable attention because it is an environment friendly process. In this review, we address the function and applications of fat-soluble vitamins, and an overview of current developments in the production of fat-soluble vitamins in transgenic plants, microalgae, and microorganisms. We focus on the metabolic and process engineering strategies for improving production of fat-soluble vitamins, and we hope this review can be useful for the people who are interested in the production of fat-soluble vitamins by biotechnological routes.
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2.
Postprandial hyperlipidemia as a risk factor in patients with type 2 diabetes.
Tomlinson, B, Chan, P, Lam, CWK
Expert review of endocrinology & metabolism. 2020;(3):147-157
Abstract
Introduction: Postprandial hyperlipidemia is a common feature of the atherogenic dyslipidemia in patients with type 2 diabetes. Quantification of this with oral fat tolerance tests is not used routinely in clinical practice and abnormal postprandial lipids are usually inferred from non-fasting plasma triglyceride levels. Identifying excessive postprandial hyperlipidemia may help to refine cardiovascular risk assessment but there are no treatments currently available which selectively target postprandial lipids and no large cardiovascular outcome trials using this as the entry criterion.Areas covered: In this review of relevant published material, we summarize the findings from the most important publications in this area.Expert opinion: Postprandial hyperlipidemia appears to contribute to the cardiovascular risk in patients with diabetes. Non-fasting triglyceride levels provide a surrogate marker of postprandial hyperlipidemia but more specific markers such as apoB48 levels may prove to be more reliable. Omega-3 fatty acids, fibrates and ezetimibe can reduce postprandial lipids but may not correct them completely. Several novel treatments have been developed to target hypertriglyceridemia and some of these may be particularly effective in improving postprandial levels. Further clinical trials are needed to establish the role of postprandial lipids in assessment of cardiovascular risk and to identify the most effective treatments.
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3.
Mango kernel fat fractions as potential healthy food ingredients: A review.
Jin, J, Jin, Q, Akoh, CC, Wang, X
Critical reviews in food science and nutrition. 2019;(11):1794-1801
Abstract
Mango kernel fat (MKF) has been reported to have high functional and nutritional potential. However, its application in food industry has not been fully explored or developed. In this review, the chemical compositions, physical properties and potential health benefits of MKF are described. MKF is a unique fat consisting of 28.9-65.0% of 1,3-distearoyl-2-oleoyl-glycerol with excellent oxidative stability index (58.8-85.2 h at 110 °C), making the fat and its fractions suitable for use as high-value added food ingredients such as cocoa butter alternatives, trans-free shortenings, and a source of natural antioxidants (e.g., sterol, tocopherol and squalene). Unfortunately, the long period of dehydration of mango kernels at hot temperature results in the hydrolysis of triacylglycerols. The high levels of hydrolysates (mainly free fatty acids and diacylglycerols) limit the application of MKF in manufacturing these food ingredients. It is suggested that the physico-chemical and functional properties of MKF could be further improved through moderated refining (e.g., degumming and physical deacidification), fractionation, and interesterification.
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4.
Does skeletal muscle carnitine availability influence fuel selection during exercise?
Stephens, FB
The Proceedings of the Nutrition Society. 2018;(1):11-19
Abstract
Fat and carbohydrate are the major fuel sources utilised for oxidative, mitochondrial ATP resynthesis during human skeletal muscle contraction. The relative contribution of these two substrates to ATP resynthesis and total energy expenditure during exercise can vary substantially, and is predominantly determined by fuel availability and exercise intensity and duration. For example, the increased ATP demand that occurs with an increase in exercise intensity is met by increases in both fat and carbohydrate oxidation up to an intensity of approximately 60-70 % of maximal oxygen consumption. When exercise intensity increases beyond this workload, skeletal muscle carbohydrate utilisation is accelerated, which results in a reduction and inhibition of the relative and absolute contribution of fat oxidation to total energy expenditure. However, the precise mechanisms regulating muscle fuel selection and underpinning the decline in fat oxidation remain unclear. This brief review will primarily address the theory that a carbohydrate flux-mediated reduction in the availability of muscle carnitine to the mitochondrial enzyme carnitine palmitoyltransferase 1, a rate-limiting step in mitochondrial fat translocation, is a key mechanism for the decline in fat oxidation during high-intensity exercise. This is discussed in relation to recent work in this area investigating fuel metabolism at various exercise intensities and taking advantage of the discovery that skeletal muscle carnitine content can be nutritionally increased in vivo in human subjects.
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5.
Preterm Human Milk Macronutrient and Energy Composition: A Systematic Review and Meta-Analysis.
Mimouni, FB, Lubetzky, R, Yochpaz, S, Mandel, D
Clinics in perinatology. 2017;(1):165-172
Abstract
This study is a systematic review of the macronutrient and energy composition of preterm human milk to enable the practicing neonatologist to make informed nutritional decisions in preterm infants. Meta-analyses were conducted in all the studies that reported total energy, true protein, fat, and lactose. Protein content decreased massively (by one-half) and significantly from day 1 to 3 at week 10 to 12. There was a significant linear increase in fat, lactose, and energy content during the same timeframe. Theoretic calculations on energy and macronutrient intake of preterm infants must be made according to a lactation time-specific manner.
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6.
The management of patients with enteric hyperoxaluria.
Asplin, JR
Urolithiasis. 2016;(1):33-43
Abstract
Enteric hyperoxaluria is a common occurrence in the setting of fat malabsorption, usually due to intestinal resection or intestinal bypass surgery. Enhanced intestinal absorption of dietary oxalate leads to elevated renal oxalate excretion, frequently in excess of 100 mg/d (1.14 mmol/d). Patients are at increased risk of urolithiasis and loss of kidney function from oxalate nephropathy. Fat malabsorption causes increased binding of diet calcium by free fatty acids, reducing the calcium available to precipitate diet oxalate. Delivery of unabsorbed bile salts and fatty acids to the colon increases colonic permeability, the site of oxalate hyper-absorption in enteric hyperoxaluria. The combination of soluble oxalate in the intestinal lumen and increased permeability of the colonic mucosa leads to hyperoxaluria. Dietary therapy consists of limiting oxalate and fat intake. The primary medical intervention is the use of oral oxalate binding agents such as calcium salts to reduce free intestinal oxalate levels. Bile acid sequestrants can be useful in patients with ileal resection and bile acid malabsorption. Oxalate degrading bacteria provided as probiotics are being investigated but as of yet, no definite benefit has been shown with currently available preparations. The current state of medical therapy and potential future directions will be summarized in this article.
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7.
The Role of Dietary Protein and Fat in Glycaemic Control in Type 1 Diabetes: Implications for Intensive Diabetes Management.
Paterson, M, Bell, KJ, O'Connell, SM, Smart, CE, Shafat, A, King, B
Current diabetes reports. 2015;(9):61
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Abstract
A primary focus of the management of type 1 diabetes has been on matching prandial insulin therapy with carbohydrate amount consumed. However, even with the introduction of more flexible intensive insulin regimes, people with type 1 diabetes still struggle to achieve optimal glycaemic control. More recently, dietary fat and protein have been recognised as having a significant impact on postprandial blood glucose levels. Fat and protein independently increase the postprandial glucose excursions and together their effect is additive. This article reviews how the fat and protein in a meal impact the postprandial glycaemic response and discusses practical approaches to managing this in clinical practice. These insights have significant implications for patient education, mealtime insulin dose calculations and dosing strategies.
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Interfacial mechanism of lipolysis as self-regulated process.
Reis, P, Watzke, H, Leser, M, Holmberg, K, Miller, R
Biophysical chemistry. 2010;(3):93-103
Abstract
Obesity is a serious public health concern with an increasing prevalence worldwide. The diet contributes strongly to this problem and high-fat food leads to unhealthy conditions. Fat digestion is an energy intensive process as it requires hydrolysis to allow the body to profit from this nutrient. This additional energy expenditure is also present in a highly redundant hormonal regulation system for fat storage which is converted in not a readily accessible form (therefore, an upstream is required in order to tackle fat-related diseases). Due to the low water solubility of oils and fats, the lipase catalyzed reactions take place at a specific locus, the oil-water interface. Despite considerable efforts in the past the effects of the interfacial composition on lipase activity have been only qualitatively understood until recently. It has recently been undertaken a detailed study of the interfacial behavior of lipases, their substrates and products which have contributed to shed light into the mechanism of lipolysis [1-4]. In addition, there are strong evidences that lipase activity is a function of interfacial composition and changes concurrently with lipolytic conversion [1]. In these cases lipase "inhibition" should be attributed to substrate depletion and not to lipase desorption or denaturation as previously hypothesized [5]. This self-limiting effect through the feedback of interfacial composition to the reaction conditions of the enzyme opens a new avenue to control lipase catalysis through the interface. A set of experiments are proposed which can be performed to further characterize and gain a deeper insight into interfacial enzymology.
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Thiazolidinediones and the liver in humans.
Yki-Järvinen, H
Current opinion in lipidology. 2009;(6):477-83
Abstract
PURPOSE OF REVIEW To review recent advances in the understanding of the mechanism of action of thiazolidinediones (TZDs) in humans. RECENT FINDINGS The liver is characterized by excess fat accumulation due to nonalcoholic causes (non-alcoholic fatty liver disease) in most patients with the metabolic syndrome and type 2 diabetes. Simple steatosis can progress to nonalcoholic steatohepatitis (NASH) and cirrhosis. Both of the commercially available antihyperglycemic TZD agonists, pioglitazone and rosiglitazone, are markedly effective in reducing liver fat content by 30-50% and sensitizing the liver to insulin. This reduces the amount of endogenous and exogenous insulin needed to inhibit hepatic glucose production. Decreases in liver fat are closely correlated with increases in serum adiponectin, which is an insulin-sensitizing adipokine produced exclusively by adipose tissue. Both TZDs are equally effective in reducing liver fat. Regarding lipid metabolism, enhanced hepatic insulin sensitivity would be predicted to lower VLDL and serum triglycerides and increase HDL-cholesterol. Pioglitazone and rosiglitazone have different effects on serum lipids, which cannot be attributed to simple insulin sensitization. Very recently, TZDs have been shown to reduce not only steatosis but possibly also hepatocellular damage in NASH. SUMMARY Given the uncertainties in benefits of TZDs in reducing cardiovascular disease in type 2 diabetes, as well as other side-effects (heart failure, fractures), TZDs may in the future be increasingly used in patients with nonalcoholic steatohepatitis.
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10.
Fat and carbohydrate metabolism during submaximal exercise in children.
Aucouturier, J, Baker, JS, Duché, P
Sports medicine (Auckland, N.Z.). 2008;(3):213-38
Abstract
During exercise, the contribution of fat and carbohydrate to energy expenditure is largely modulated by the intensity of exercise. Age, a short- or long-term diet enriched in carbohydrate or fat substrate stores, training and gender are other factors that have also been found to affect this balance. These factors have been extensively studied in adults from the perspective of improving performance in athletes, or from a health perspective in people with diseases. During the last decade, lifestyle changes associated with high-energy diets rich in lipid and reduced physical activity have contributed to the increase in childhood obesity. This lifestyle change has emerged as a serious health problem favouring the early development of cardiovascular diseases, insulin resistance or type 2 diabetes mellitus. Increasing physical activity levels in young people is important to increase energy expenditure and promote muscle oxidative capacity. Therefore, it is surprising that the regulation of balance between carbohydrate and lipid use during exercise has received much less attention in children than in adults. In this review, we have focused on the factors that affect carbohydrate and lipid metabolism during exercise and have identified areas that may be relevant in explaining the higher contribution of lipid to energy expenditure in children when compared with adults. Low muscle glycogen content is possibly associated with a low activity of glycolytic enzymes and high oxidative capacity, while lower levels of sympathoadrenal hormones are likely to favour lipid metabolism in children. Changes in energetic metabolism occurring during adolescence are also dependent on pubertal events with an increase in testosterone in boys and estrogen and progesterone in girls. The profound effects of ovarian hormones on carbohydrate and fat metabolism along with their effects on oxidative enzymes could explain that differences in substrate metabolism have not always been observed between girls and women. Finally, although the regulatory mechanisms of fat and carbohydrate balance during exercise are quite well identified, there are a lack of data specific to children and most of the evidences reported in this review were drawn from studies in adults. Isotope tracer techniques and nuclear magnetic resonance will allow non-invasive investigation of the metabolism of the different substrate sources in skeletal muscle.